>> reporter: scott, we'd like to show you the current makeup of the u.s. senate. there are 53 democrats, 47 republicans. one-third of the senate is up for election tonight. in order for republicans to take back control of the senate, they would need to win four seats. that battle will take place in about a dozen states from places like massachusetts and connecticut out east to nevada and arizona out west. cbs news considers six of these states to be true tossups. that's massachusetts, connecticut, virginia, wisconsin, north dakota, and montana. now let's take a look at the house of representatives. every two years all 435 seats in the house come up for election. currently there are 242 republicans, 193 democrats. in order for democrats to take back control of the house, they would need to win 25 seats. we've talked to a number of democrats privately who say that's going to be all but impossible for them so it looks like republicans will control the house, but the makeup of the chamber could well change. currently there are 27 hispanics in the house of representati